Steel 1045 properties
AISI 1045 steel is a medium-hardenability carbon steel, typically supplied in hot-rolled or normalized condition. Its tensile strength ranges from 570 to 700 MPa and Brinell hardness from 170 to 210 in those states. It offers a good balance of mechanical strength, toughness, and machinability, making it a frequent choice for components subjected to moderate stresses in the automotive, machinery, and capital goods industries.
Designation and equivalent standards
Section titled “Designation and equivalent standards”AISI/SAE 1045 steel has direct equivalents in other international standards:
| Standard | Designation |
|---|---|
| EN | C45 (1.0503), C45E (1.1191), C45R (1.1201) |
| DIN | Cm45, C45K, C45E |
| AFNOR | XC48H1, XC48 |
| UNI | C45 |
| UNE | C45E, C45K |
| JIS | S45C |
Chemical composition
Section titled “Chemical composition”The typical composition of 1045 steel, according to AISI, is as follows (ladle analysis):
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.42 – 0.50 |
| Manganese (Mn) | 0.60 – 0.90 |
| Phosphorus (P) max. | 0.040 |
| Sulfur (S) max. | 0.050 |
| Iron (Fe) | Balance (≈98.5 – 98.98) |
Due to the absence of significant alloying elements, 1045 does not respond to nitriding treatments; its hardening is achieved by quenching and tempering, or by surface hardening via induction or flame.
Mechanical properties in as-supplied condition
Section titled “Mechanical properties in as-supplied condition”The values below correspond to hot-rolled or normalized material (fine grain size), measured at room temperature.
| Property | Metric | Imperial |
|---|---|---|
| Brinell hardness | 163 – 210 | 163 – 210 |
| Rockwell B hardness | 84 – 93 | 84 – 93 |
| Tensile strength | 565 – 585 MPa | 82 000 – 85 000 psi |
| Yield strength (0.2 %) | 310 MPa | 45 000 psi |
| Elongation in 50 mm | 16 % | 16 % |
| Reduction of area | 40 % | 40 % |
| Modulus of elasticity | 200 – 205 GPa | 29 000 – 29 700 ksi |
| Shear modulus (typical) | 80 GPa | 11 600 ksi |
| Poisson’s ratio | 0.29 | 0.29 |
The strength data come from verified sources (Azom, Engineering Toolbox) and represent typical values for sections up to 60 mm.
Mechanical properties after quenching and tempering
Section titled “Mechanical properties after quenching and tempering”1045 steel can significantly improve its strength through heat treatment, although the hardening depth is limited. Properties depend on the tempering temperature:
| Condition | Hardness (HRC) | Tensile strength (MPa) | Yield strength (MPa) | Elongation (%) |
|---|---|---|---|---|
| Water quench + temper at 200 °C | 54 – 60 | 1 300 – 1 500 | 1 100 – 1 260 | 5 – 8 |
| Water quench + temper at 400 °C | 40 – 46 | 950 – 1 100 | 820 – 950 | 9 – 12 |
| Water quench + temper at 600 °C | 28 – 33 | 700 – 850 | 500 – 620 | 15 – 18 |
| Surface hardening (induction/flame) | 54 – 60 (surface) | – | – | – |
Water or brine quenching is performed from 820–850 °C. For parts with sections larger than about 60 mm, core hardening is incomplete, so surface hardening is used when only wear resistance on the outer layer is required.
Physical properties
Section titled “Physical properties”| Property | Value |
|---|---|
| Density | 7.85 – 7.87 g/cm³ |
| Melting point | ~ 1460 – 1520 °C |
| Specific heat | 486 J/(kg·K) at room temperature |
| Thermal conductivity | 49.8 W/(m·K) at 20 °C |
| Coefficient of thermal expansion | 11.7 × 10⁻⁶ / °C (20–300 °C) |
The mass density is considered 0.284 lb/in³ in imperial units.
Thermal properties
Section titled “Thermal properties”Heat treatments influence the microstructure and therefore the thermal properties. Below are typical values for normalized states:
| Property | Value |
|---|---|
| Maximum service temperature in oxidizing atmosphere | 500 – 650 °C (intermittent) |
| Austenitizing temperature for quenching | 820 – 850 °C |
| Recommended tempering temperature | 150 – 650 °C, according to requirement |
Above approximately 650 °C, the mechanical strength drops sharply, so continuous high-temperature use requires considering other grades (e.g., Cr-Mo alloy steels).
Recommended heat treatments
Section titled “Recommended heat treatments”| Process | Heating (°C) | Soaking | Cooling |
|---|---|---|---|
| Forging | 850 – 1250 | Until uniform | In furnace or air (depending on size) |
| Annealing | 800 – 850 | Uniformity + 1 h per 25 mm | In furnace |
| Normalizing | 870 – 920 | 10 – 15 min per 25 mm | Still air |
| Stress relieving | 550 – 660 | 1 h per 25 mm | Still air |
| Quenching | 820 – 850 | 10 – 15 min per 25 mm | Water, brine or fast oil |
| Tempering | 400 – 650 (according to hardness) | 1 h per 25 mm thickness | Still air |
Direct quenching from forging temperature is not recommended; prior normalizing to refine the grain is necessary.
Weldability and machinability
Section titled “Weldability and machinability”- Weldability: The carbon content (0.42–0.50 %) makes welding of 1045 require preheating (150–300 °C) and slow cooling to avoid cracks in the heat-affected zone. Low-hydrogen electrodes are recommended and, whenever possible, normalize after welding.
- Machinability: The machinability index is around 55–60 % taking SAE 1112 steel (100 %) as reference. It is easily machined in normalized or hot-rolled condition; threading and deep drilling operations can be improved by prior annealing.
Typical applications by industry
Section titled “Typical applications by industry”Thanks to its cost‑strength ratio, 1045 steel is used in a wide variety of components:
| Industry | Typical parts and components |
|---|---|
| Automotive and transportation | Axles, crankshafts, connecting rods, half-shafts, torsion bars |
| General machinery | Medium-sized gears, pinions, spindles, guides, bushings |
| Tools | Holding fixtures, jaws, low-production dies, simple drills |
| Construction | High-strength bolts, studs, pins, dowels |
| Hydraulic industry | Pistons, cylinder rods, flanges |
1045 steel is especially suitable for parts requiring induction or flame surface hardening to improve wear resistance without increasing material cost.
Comparison with similar steels
Section titled “Comparison with similar steels”| Grade | Carbon (%) | Alloying elements | Typical tensile strength (MPa) | Hardenability | Relative cost | Machinability |
|---|---|---|---|---|---|---|
| AISI 1040 | 0.37 – 0.44 | None | 520 – 650 | Low | Low | 60 % |
| AISI 1045 | 0.42 – 0.50 | None | 565 – 700 (untreated) | Medium‑low | Low | 55 – 60 % |
| AISI 1060 | 0.55 – 0.65 | None | 650 – 800 | Medium | Low | 50 % |
| AISI 4140 | 0.38 – 0.43 | Cr, Mo | 750 – 950 (quenched and tempered) | High | Moderate | 55 % |
| AISI 1141 | 0.37 – 0.45 | Mn 1.35‑1.65 + S | 600 – 750 | Medium‑low | Low | 65 – 70 % |
Interpretation:
- Compared to 1040, 1045 offers higher strength and surface hardness, but slightly lower toughness.
- 1060 achieves higher strength after quenching, but with more limited weldability and machinability.
- 4140, being a Cr‑Mo alloy steel, allows complete hardening in thicker sections (up to 75‑100 mm) and retains high toughness; however, its cost is higher.
- 1141 improves machinability due to sulfur addition, although it slightly reduces toughness.
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the maximum tensile strength that 1045 steel can achieve?
Section titled “What is the maximum tensile strength that 1045 steel can achieve?”The maximum tensile strength can exceed 1 300 MPa when water quenching and low tempering (~200 °C) are applied, reaching values up to 1 500 MPa in thin sections.
What surface hardness is obtained by induction hardening?
Section titled “What surface hardness is obtained by induction hardening?”Induction or flame surface hardening allows hardness of 54 to 60 HRC on the outer layer, depending on part size, heating rate, and quenchant used.
Up to what thickness can the core of a 1045 part be fully hardened?
Section titled “Up to what thickness can the core of a 1045 part be fully hardened?”The hardening penetration is limited: the core can be uniformly hardened in thicknesses up to 60 mm, beyond which the martensitic transformation is incomplete and core hardness drops significantly.
At what temperature should 1045 steel be forged?
Section titled “At what temperature should 1045 steel be forged?”Forging is carried out in the range of 850 °C to 1 250 °C, ensuring uniform temperature and avoiding heating below 850 °C during deformation to prevent crack formation.
What tempering temperature provides approximately 700 MPa strength?
Section titled “What tempering temperature provides approximately 700 MPa strength?”To obtain a tensile strength close to 700 MPa, 1045 steel should be tempered in the range of 580 – 620 °C, holding at least 1 hour per 25 mm thickness and cooling in air.
What is the thermal conductivity of 1045 steel at room temperature?
Section titled “What is the thermal conductivity of 1045 steel at room temperature?”The thermal conductivity of 1045 steel at 20 °C is approximately 49.8 W/(m·K), a value that decreases as working temperature increases.
Limitations and warnings
Section titled “Limitations and warnings”- Not suitable for cryogenic applications or corrosive environments without protective coating.
- Weldability, although possible with controlled procedures, requires qualified personnel to avoid hydrogen embrittlement.
- The mechanical property values after quenching and tempering are approximate and strongly depend on part geometry, cooling medium, and heat treatment shop practice.
- Not recommended for use in as-forged condition without subsequent normalizing or quench and tempering treatment.
References
Section titled “References”- azom.com: https://www.azom.com/article.aspx?ArticleID=6130
- engineeringtoolbox.com: https://www.engineeringtoolbox.com/engineering-materials-properties-d_1225.html
- steelnumber.com: https://www.steelnumber.com/en/equivalent_steel_iron_eu.php?zname_id=138